Centrifugal casting machine having molten metal level detector

ABSTRACT

A centrifugal casting machine includes upper and lower rotatable axially movable coaxial clamp members the lower clamp member being engageable and disengageable with a drive motor. An indexing table conveys successive split centrifugal molds having upper central sprues and conductor members on their underfaces between the clamps. A molten metal reservoir is located above the clamps and has a valved nozzle directed to a hollow shaft of the top clamp which has at its bottom a pair of spaced electrodes. A swingable plate is located next to the table proximate the clamps. A control network including sensing switches and actuating devices is provided for raising the lower clamp to clamp the mold to the upper clamp, the restricting raising of the upper clamp causing the drive coupling between the motor and the lower clamp and thereafter the opening of the reservoir valve. Upon filling of the mold as sensed by the electrodes the valve is closed, the motor then disengaged and the lower clamp lowered. The sensing elements are shorted by an inverted mold conductor member to prevent valve opening, the absence of a mold as sensed by the excessive raising of the lower clamp terminates the cycle as does the sensing of metal centrifugally flung from the mold.

iJite States Patent [191 Pertot [451 Aug. 14, 1973 CENTRIFUGAL CASTING MACHINE HAVING MOLTEN METAL LEVEL DETECTOR [76] Inventor: Alfred G. Pertot, 2 Yale Rd.,

Merrick, NY. 11566 [22] Filed: 23, 1971 [21] Appl. No.: 211,268

Primary Examiner-R. Spencer Annear AnorneyStanley Wolder [5 7] ABSTRACT A centrifugal casting machine includes upper and lower rotatable axially movable coaxial clamp members the lower clamp member being engageable and disengageable with a drive motor. An indexing table conveys successive split centrifugal molds having upper central sprues and conductor members on their underfaces between the clamps. A molten metal reservoir is located above the clamps and has a valved nozzle directed to a hollow shaft of the top clamp which has at its bottom a pair of spaced electrodes. A swingable plate is located next to the'table proximate the clamps. A control network including sensing switches and actuating devices is provided for raising the lower clamp to clamp the mold to the upper clamp, the restricting raising of the upper clamp causing the drive coupling between the motor and the lower clamp and thereafter the opening of the reservoir valve. Upon filling of the mold as sensed by the electrodes the valve is closed, the motor then disengaged and the lower clamp lowered. The sensing elements are shorted by an inverted mold conductor member to prevent valve opening, the absence of a mold as sensed by the excessive raising of the lower clamp terminates the cycle as does the sensing of metal centrifugally flung from the mold.

17 Claims, 11 Drawing Figures Patented Aug. 14, 1973 5 Sheets-Sheet 1 l NV ENTOR flz/aefn 6. Pfemr Q/ Patented Aug. 14, 1973 5 SheetsSheet 2 T y a 00 R Y 7 & M m m W9. T 7F w M W Patented Aug. 14,1973 3,752,214.-

5 Sheets-Sheet 4 INVENTOR ATT RNEY 44/6950 6. Pier-4r Patented Aug. 14, 1973 3,752,214

5 Sheets-Sheet l RE E FEL/ 3} T/MER INVENTOR flu? 0 @Paemr ATTORNEY CENTRIFUGAL CASTING MACHINE HAVING MOLTEN METAL LEVEL DETECTOR BACKGROUND OF THE INVENTION The present invention relates generally to improvements in casting equipment and it relates particularly to an improved automatic centrifugal casting machine.

A conventional method casting low melting point metals is by means of centrifugal casting. Generally this method employs a horizontally split rubber mold having a central sprue with runners extending radially to the cavities which may have complex surfaces adapting the centrifugal casting process to correspondingly complex shapes. The apparatus commonly employed in centrifugal casting of metals possesses numerous drawbacks and disadvantages. Its use is frequently hazardous and generally requires the continuous attendance of a highly skilled operator who controls all the operations of the procedure including the rotation of the mold, the ladling of metering of the molten metal into the mold, etc. Consequently, the articles cast with conventional centrifugal casting equipment are expensive by reason of the high labor costs and are frequently of low and non-uniform quality by reason of the lack of close process control. The conventional centrifugal casting equipment thus leaves much to be desired.

SUMMARY OF THE INVENTION locked sequence.

A further object of the present invention is to provide an improved automatic centrifugal casting machine in which improper handling or manipulation is prevented.

Still a further object of the present invention is to provide an improved centrifugal casting machine of the above nature characterized by the reliability, rugged ness, versatility, adaptability and ease of operation.

The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawings which illustrate a preferred embodiment thereof.

In a sense the present invention contemplates the provision of a centrifugal casting machine comprising a centrifugal casting mold having a central sprue a rotatable support member separably supporting the mold for rotation therewith about a vertical axis, a molten metal reservoir having an outlet nozzle directed downward toward the sprue, a valve for opening and closing the nozzle, means for sensing the metal in the mold, and valve control means responsive to the sensing means for closing the valve.

In the preferred form of the present apparatus there are provided top and bottom rotatable coaxial clamp member, the upper clamp member being coaxially moveable a limited distance and means being provided for raising the lower clamping member. A first switch senses the raising of the first clamp member above a predetermined level and a second switch senses the raising of the second clamp member. The first clamp member is driven by way of a disengageable friction drive by an electric motor. A molten metal reservoir is located above the second clamp member and is provided with a nozzle directed to a hollow shaft supporting the second clamp member and having a piston controlled valve. A pair of metal sensing electrodes are located at the bottom of the hollow shaft. An indexing table advances successive centrifugal molds between the clamp members and a switch actuating plate is located along the table proximate the clamp members to sense the escape of metal from the rotating mold. A conducting disc is positioned on the bottom of each mold. A sequencing network raises the first clamp member to raise the second clamp member in the presence of a mold and the actuated second switch causes the driving of the clamped mold and the opening of the nozzle valve which is closed upon filling of the mold in response to the sensing electrodes. The operating cycle is interrupted or terminated upon actuation of the first switch or the third switch and an inverted clamp mold prevents the nozzle valve opening.

The improved centrifugal casting machine is rugged, reliable, highly versatile and adaptable, and requires a minimum of skilled labor and is easy, safe and simple to operate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary front elevational view, partially in section, of an apparatus embodying the present invention, shown in its rest position;

FIG. la is an enlarged sectional view taken along line la la in FIG. 1;

FIG. 2 is a fragmentary view similar to FIG. I, the apparatus being illustrated during a normal operating cycle;

FIG. 3 is an enlarged sectional view taken along line 3 3 in FIG. 1;

FIG. 4 is an enlarged fragmentary vertical sectional view of a section of the apparatus in the position shown in FIG. 1;

FIG. 5 is a view similar to FIG. '4 with the apparatus illustrated during a casting cycle;

FIG. 6 is a view taken along lines 6 6 in FIG. 5;

FIG. 7 is a fragmentary medial sectional view of a filled centrifugal mold employed with the present apparatus; 7

FIG. 8 is an exploded front perspective view of the apparatus metal sensing electrodes;

FIG. 9 is a transverse sectional view of a centrifugal mold larger than that earlier illustrated and the associated support structure; and

FIG. 10 is a schematic diagram of the apparatus control network.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings which illustrate a preferred embodiment of the present invention, the reference numeral 10 generally designates the improved centrifugal casting machine which includes a lower horizontal base plate 11 suitably mounted atop depending legs 12 A lower horizontal mounting plate 13 is rigidly suspended below base plate 1 by vertical hanger rods 14. Vertically axially aligned upper and lower ball bearing members 16 and 17 respectively register with corresponding openings in and are affixed to plates 11 and 13, each of the ball bearing members 16 and 17 having an axial slide bushing 18 fixed therein.

Slideably engaging and projecting through bushing 18 is a vertical shaft 29 having an elongated longitudinal groove or keyway 20 extending from a point below the top of shaft 20. A fly wheel 21 having a cylindrical friction outerface 22 is provided with a hub 23 with end faces entrapped between the confronting ends of bushing 18. A key 24 engages a keyway in hub 23 and slideably engages keyway 20 so that shaft 19 rotates with and is axially slideably in flywheel 21. A circular clamp plate 26 having a centrally located upwardly directed mold plate positioning pin 27 which is bevelled at its top is coaxially mounted atop shaft 29 and is keyed thereto for rotation with shaft 19.

A horizontal bracket 28 is positioned below and supported from mounting plate 13 by hanger rod and in turn supports a depending double ended air or hydraulic cylinder 29 which is coaxial with shaft 19 and is-connected through an associated solenoid actuated four way valve, in the known manner, to a pressurized fluid source. The shaft 19 is connected by a coupling member 30 having top and bottom peripheral shoulders to the piston rod 32 of air or hydraulic cylinder 29. Upper and lower shaft position sensing switches SW6 and SW5 are mounted on a rod 25. Upper switch SW6 includes an actuating arm SW6a located in the vertical path of coupling 30 and lower switch SW5 includes an articulated actuating pawl arm SWSa oriented to be actuated only by the downward bearing of coupling member 30 thereon.

A vertical mounting plate 33 depends from and is supported by base plate 11 for swinging abouta horizontal transverse axis proximate the upper edge of plate 33 and is laterally offset from wheel 21. The angular position of plate 33 is controlled by a air or hydraulic cylinder 34 which is connected between a proximate rod 25 and the plate 33 and is connected to a pressurized fluid by an associated four way solenoid actuated valve. Mounted on the upper inside face of plate 33 is a bearing block 36 which rotatably supports a vertical shaft having a friction drive wheel 37 fixed to its top end at the level of wheel 21 and a pulley 38 fixed to its bottom end. An electric motor 39 having a vertical drive shaft is mounted on the lower outside face of plate 33 and a pulley 40 is fixed to the motor drive shaft and coupled to pulley 38 by a drive belt 41. When cylinder 34 is actuated to advance swing plate 33 to the left, as viewed in FIG. 2, friction wheel 37 drive engages wheel surface 22 and when cylinder 34 is actuated to retract plate 33 to the right wheels 21 and 37 are disengaged. SA switch SW4 has an actuating arm located in the path of plate 33 to be actuated upon retraction of plate 33 as shown in FIG. 1.

An upper horizontal base plate 42 is supported above base plate 1 l by poses 43 mounted on base plate 11. A circular opening is formed in plate 42 coaxial with shaft 29 and is lined with abearing bushing 44. A hollow rotable shaft member 46 is rotatably and slideably engaged by and projects through bushing 44 and terminates at its bottom in a peripheral flange 47 positioned below plate 42 and has an enlarged integrally formed cylindrical section 48 which normally rests on plate 42.

A thrust bearing 49 engages the lower part of shaft 46 and rests on plate 42, the upper face of thrust bearing 49 normally being below the underface of plate 42 to permit the limited upward movement of shaft 46 and head 48. Secured to flanges 47 and coaxial with shafts 46 and 19 is a circular upper clamp plate 50 having a central circular opening of the same diameter and registering with the bore of shaft 46 and provided with a depending peripheral lip 51.

The bore of shaft 46 is lined with a heat stable tubular member 52 formed of an electrical insulating, high melting point material which may be a refractory, a thermoset resin or a high melting point resin and extends from the bottom face of clamp plate 50 to a point above the top of shaft 46. A pair of electrode members 53 and 54 are partially embedded in tube 52. The electrode member 54 includes a top annular slip ring 56 which engages a peripheral groove in tube 52 above shaft 46 and is separated from the top shaft 46 by an insulator washer 57. A plurality of circumferentially spaced electrode defining vertical bars 58 depend from and are integrally formed with ring 56 and are embedded in liner 52 extending to and having their bottom faces exposed at the bottom of tube 52. The electrode member 53 includes a top annular slip ring 59 which engages a peripheral groove in tube 52 above slip ring 56 and is of smaller diameter than and separated from slip ring 56 by a peripheral flange 60 integrally formed with tube 52. A plurality of circumferentially spaced electrode defining vertical bars 61 depend from and are integrally formed with ring 59 and are embedded in tube 52 at positions inwardly and circumferentially offset from bars 58 and extend to and have their bottom faces exposed at the bottom of tube 52. The slip rings 56 and 59 are engaged by stationary brushes 63 and 64 respectively. A switch SW3 is mounted on plate 42 proximate shaft head 48 and includes an actuating arm 65 provided with a follower engaging the top face of head 48 so that the raising thereof with the raising of upper clamp plate 50 actuates switch SW3.

Mounted on base plate 42 and spaced above shaft 46 by means of support brackets 66 is a molten metal reservoir 67 of any suitable construction, preferably provided with heat insulating walls and electric or gas heaters which are thermostat controlled to maintain the contained metal M in the desired molten state, as is well known. A vertical nozzle 68 coaxial with and directed toward tubular liner 52 extends through the bot tom wall 69 of reservoir 67 and terminates at its top, shortly above bottom wall 69, in a flared valve seat 70. A frusto-conical valve member 71 separably engages valve seat and is connected to the bottom of an axially movable vertical rod 72 which projects through an opening in the top wall or reservoir'67. A lever 73 is swingably mounted atop reservoir 67 by a bracket 74 and has a slotted first end engaging a pin 76 located on the upper end of rod 72 and an opposite end pin connected to the piston rod 76 of a double acting vertical air or hydraulic cylinder 77 provided with a solenoid actuated four way valve which connects the cylinder to a pressurized fluid or air source. The bottom of cylinder 77 is pivotly connected to a mounting bracket 78 located on base plate 42.

In' order to advance successive molds into aligned registry between clamp plates 26 and 50 there is provided a circular indexing table 79 which includes a rotatable flat circular base plate 80 centrally mounted at the top of a shaft 81 which is suitably journalled to the top and bottom circular plates 82 and 83 of'a support frame located on base plate 11. The plates 82 and 83 are separated and joined to the top and bottom faces of a cylindrical wall 84 having a side opening 86, top plate 82 being coaxial with and underlying table plate 80. A plurality of regularly circumferentially spaced circular openings 87 are formed in base plates 80, inwardly directed peripheral lips 88 being formed at the bottom of each opening 87. The shaft 81 and plate 80 are so located and the openings 87 so positioned that the locus or path of the centers of openings 87 intersects the axis of clamp plates 26 and 51 between the clamp plates.

A vertical polygonal wall 89 projects upwardly from plate 80 and is concentric therewith and vertical partition walls 90 extend radially from the comers of wall 89 midway between successive openings 87 to define with the slides of polygonal wall 89 individual compartments 91 for each opening 87. Separably nesting in each of the openings 87 and resting on a lip 88 is a circular mold support plate 92 having a central opening 94 mating clamp plate positioning pin 27. One face of support plate 92 is flat and the other face thereof has a shallow coaxial circular well 96 formed therein of the diameter of clamp plate 26 and with a bevelled peripheral wall so that the support plate 92 accommodates molds of different diameters.

A double acting horizontal cylinder 97 connected to a pressurized fluid source by a solenoid actuated four way valve is mounted on plate 83 transversely offset from shaft 81. A ratchet wheel 98 is affixed to shaft 81 and has a number of teeth 99 equal to the number of index table openings 87. A block 100 is mounted at the end of the piston rod 101 of cylinder 97 and a pawl 102 is mounted on block 100 for restricted rocking and is spring urged to a retracted position and cooperates with ratchet wheel 97 to advance the ratchet wheel an increment correspondong to the angle between successive teeth 98 with the retraction of piston rod 101 and slips by the ratchet wheel 97 with the advance of the piston rod 101. The ratchetwheel 97 and the indexing table base 80 are so related that upon each increment retraction of the piston rod 101 the index table 79 is rotated by the pawl and ratchet to advance a successive opening 87 into axial alignment with clamp plates 26 and 50.

A switch SW2 is supported on plate 83 and includes an actuating arm SW2a located in the path of a pin 103 mounted on block 100 so as to actuate switch SW2 upon retraction of pawl block 100. An arcuate plate 104 depending from plate 102 extends along and outside the periphery of index table plate 80 in the area of the casting zone proximate clamp plates 26 and 50 and closes the end of a compartment 91 in the rest position of the index table 79. A sensing panel 106, similar in shape to plate 104 is positioned radially inwardly of and is coextensive with plate 106 and is supported for radial movement and engages the actuating plunger SW7a of a switch SW7. The plate 106 is normally resiliently urged radially inwardly and is urged outwardly by the impact thereon by metal released from a rotating mold engaged between clamps 26 and 50 to a actuate switch SW7.

A plurality of rubber centrifugal molds 107 of generally conventional construction are provided, each mold 107 being horizontally split into separable upper and lower sections 108 and 109 and being of shallow cylindrical shape. The mold sections define a plurality of cavities 110 connected by radial runners 111 with a central sprue 112 in the mold top section 108. The

sprue 112 is of a diameter slightly less than the inside diameter of shaft 46 and the diameter of the mold 107 is advantageously equal to that of support plate 92 or the well 96 therein. The underface of the bottom mold section 109 is covered with an adherent layer 1 13 of an electrically conducting material, for example, metal foil, which should cover at least the center of the underface of a diameter at least equal to that of sprue 112.

Referring now to FIG. 10 which illustrates the apparatus cycle sequence and safety control network a hand operated start switch SW8 is connected to the valve actuating solenoid of cylinder 97 in a manner that the actuation of switch SW8 causes the extension of piston 101, and the switch SW2 which is actuated with the piston extension is connected to the solenoid valve of piston 29 so that actuation of switch SW2 effects the rais' ing of the piston 32 of cylinder 29. The switch SW5 is connected to the valve solenoid of cylinder 97 so its actuation extends piston 101 and switch SW6 is connected to the valve solenoids of cylinders 97 and 29 so that actuation of switch SW6 causes the pistons thereof to retract and lower respectively. The switch SW4 is connected through a suitable adjustable timer network A to the valve solenoids of cylinders 29 and 97 to depress the piston of cylinder 29 and retract piston 101 at an adjustable predetermined interval following the actuation of switch SW4.

The switch SW3 is connected through a time delay network B to the solenoid valve of cylinder 77 and directly to the solenoid valve of cylinder 34 so that the actuation of switch SW3 first effects retraction of the piston or cylinder 34and then effects the lowering of piston 76 of cylinder 77 and the opening of valve 71 a predetermined interval after such actuation. The solenoid of a relay C is connected through the secondary of a step down transformer T between the electrodes 53 and 54 and the normally open switch SW7 is connected between electrodes 53 and 54, the primary of transformer T being connected to an AC current source. The output of relay C is connected so that upon energization of its solenoid the valve solenoid of cylinder 77 is actuated to raise pistonrod 76 to close valve 71 and the valve solenoid of cylinder 34 is actuated to swing mount plate 33 to the right as viewed in FIG. 1.

In the operation of the apparatus 10 the operator places a closed empty mold 107 .onto each successive support plate 92 in the well 96 or on the opposite flat face thereof, depending on the mold size, as'a corresponding compartment 91 is brought to rest at the loading and unloading station, and as the filled mold enters the station he replaces the filled mold with an empty mold and removes the casting from the filled mold. The casting cycle is initiated by the actuation ,of either switch SW8 or switch SW5upon the lowering of the piston 32 of cylinder 29 whereby to actuate cylinder 97 to advance pawl 102 and advance the index table 79 an increment by way of ratchet wheel 97, the extended pawl block actuating switch SW2, to thereby transport an empty mold between the clamp plates 26 and 50. The actuated switch SW2 causes cylinder 29 to raise clamp plate 26 and clamp a mold 1 07 to clamp plate 50, raising the latter to actuate switch SW3. The actuation of switch SW3 causes cylinder 34 to swing friction wheels 37 and 21 into engagement to rotate the clamp plates and mold, and after a short delay as effected by network B cylinder 77 is actuated to open valve 71 and permit the flow of molten metal M through nozzle 68 and tubular liner 52 into the mold sprue 112. With the filling of the mold with molten metal it reaches the level of electrodes 58 and 61 to short the electrodes and actuate the relay C which in turn causes cylinder 77 to raise piston 76 and close valve 71 and stop the flow of metal and causes cylinder 34 to advance its piston and effect the disengagement of wheels 21 and 37 and the actuation of switch SW4. The actuated switch SW4, after an interval determined by timer A. causes the lowering of clamp plate 26 by cylinder 29 and the retraction of pawl 102 by cylinder 97. The lowering of the clamp member 26 effects the actuation of switch SW to cause the initiation of another cycle as above.

In the event that no mold is located on the rising clamp plate 26, piston rod 32 and member 30 will be raised above their normal level to actuate switch SW6 which will cause the lowering of clamp plate 26 and the retraction of pawl 102 by piston rod 101 and the lowering member 30 will actuate switch SW5 to start another cycle. If a mold is deposited upside down in a compartment, when it is clamped between clamp plates 26 and 50 electrodes 58 and 61 will be shorted by conducting layer 1 13 to keep valve 71 closed, disengage wheels 21 and 37 and switch SW4 will be actuated to return to apparatus to its initial position and initiate another cycle. The escape of metal from the rotating mold will result in the closing of switch SW7 by the impact of the metal on panel 106 to effect the closing of valve 71 and the termination of the cycle and the initiation of the next cycle in the manner described when the electrodes 53 and 54 are shorted.

While there has been described and illustrated a preferred embodiment of the present invention it is apparent that numerous alterations omissions and additions may be made without departing from the spirit thereof.

What is claimed is:

l. A centrifugal casting machine comprising a centrifugal casting mold having a vertically extending central sprue, a rotatable support member separably supporting said mold for rotation therewith about a vertical axis, a molten metal reservoir having an outlet nozzle directed downwardly toward said sprue, a valve for opening and closing said nozzle, means for sensing the metal in said mold including a pair of spaced electrodes mounted for rotation about said axis while being in vertical registry with said sprue and transversely offset from the vertical axis thereof and valve control means responsive to the electrical resistance between said electrodes for closing said valve when molten metal shorts said electrodes.

2. The casting machine of claim 1 including a clamp member positioned above said support member and coaxially rotatable therewith and having an axial passageway providing communication between said sprue and said nozzle, and means for raising and lowering said support member to respectively clamp and release said mold between said support member and clamp member.

3. The casting machine of claim 2 said electrodes being supported with said support member and registering with said sprue proximate the level of the top opening thereof.

4. The casting machine of claim 3 including a conductor positioned on the underface of said mold and adapted to engage said electrodes upon the raising of said mold in an inverted position. v

5. The casting machine of claim 2 comprising means responsive to the raising of said clamp member for opening said valve.

6. The casting machine of claim 2 including a motor driven member movable into drive engagement and disengagement with said support member, and means responsive to the raising of said clamp member-for urging said drive member to its engaged position.

7. The casting machine of claim 1 including a horizontal indexing table rotatable about a vertical axis eccentric to that of said support member and having circumferentially spaced openings successively movable into registry and above said support member, a centrifugal mold separably registering with each of said openings and means for raising and lowering said support member to respectively raise and return a registering mold to said indexing table.

8. The casting machine of claim 6 comprising a circular plate separably resting on said table in registry with each opening therein, said molds coaxially separably resting on said plates.

9. A centrifugal casting machine comprising a vertically movable, rotatable lower clamp member, an upper clamp member positioned above said lower clamp member and rotatable coaxially with said lower clamp member and having an axial passageway therethrough, a plurality of centrifugal molds having axial sprues in the upper sections thereof, a horizontally rotatable indexing table separably supporting said molds in circumferentially spaced relationship and movable between said clamp members for conveying successive molds into coaxial registry between said clamp members, a molten metal reservoir located above said upper clamp member, nozzle communicating with said reservoir and directed toward said passageway, a valve for opening and closing said nozzle, a drive means movable between drive engagement and disengage position with said lower clamp member, and cycle sequencing means including first means for sensing the raising of said lower clamp member and the clamping of a mold between said clamp members, second means for sensing the metal level in a clamped mold, means responsive to the actuation of said first means for shifting said drive means into engage position and opening said valve, means responsive to the actuation of said second means for closing said valve and shifting said drive means to disengage position and lower said lower clamp member.

10. The centrifugal casting machine of claim 9 wherein said second clamp member is vertically movable between raised and normally depressed positions, and said first sensing means is responsive to the raising of said upper clamp member.

11. The centrifugal casting machine of claim 9 including a vertical hollow shaft. supporting said upper clamp member and having an axial bore delineating said passageway, said first sensing means including a pair of spaced electrodes positioned at the level of the underface of said upper clamp member in registry with said sprue.

12. The centrifugal casting machine of claim 9 including means responsive to the raising of said lower clamp member above a predetermined level for bypassing the opening of said valve terminating said cycle.

13. The centrifugal casting machine of claim 9 including third means located proximate the border of a clamped mold response to the ejection of metal from at the periphery of said table.

16. The centrifugal casting machine of claim 9 including a cylindrically shaped plate located along the periphery of said table proximate said clamp members and being outwardly movable and means responsive to the outward movement of said plate for closing said nozzle valve.

17. The centrifugal casting machine of claim 9 including means positioned on the underface of said molds for actuating said second means when an inverted mold is engaged between said clamp members. I! l i l 

1. A centrifugal casting machine comprising a centrifugal casting mold having a vertically extending central sprue, a rotatable support member separably supporting said mold for rotation therewith about a vertical axis, a molten metal reservoir having an outlet nozzle directed downwardly toward said sprue, a valve for opening and closing said nozzle, means for sensing the metal in said mold including a pair of spaced electrodes mounted for rotation about said axis while being in vertical registry with said sprue and transversely offset from the vertical axis thereof and valve control means responsive to the electrical resistance between said electrodes for closing said valve when molten metal shorts said electrodes.
 2. The casting machine of claim 1 including a clamp member positioned above said support member and coaxially rotatable therewith and having an axial passageway providing communication between said sprue and said nozzle, and means for raising and lowering said support member to respectively clamp and release said mold between said support member and clamp member.
 3. The casting machine of claim 2 said electrodes being supported with said support member and registering with said sprue proximate the level of the top opening thereof.
 4. The casting machine of claim 3 including a conductor positioned on the underface of said mold and adapted to engage said electrodes upon the raising of said mold in an inverted position.
 5. The casting machine of claim 2 comprising means responsive to the raising of said clamp member for opening said valve.
 6. The casting machine of claim 2 including a motor driven member movable into drive engagement and disengagement with said support member, and means responsive to the raising of said clamp member for urging said drive member to its engaged position.
 7. The casting machine of claim 1 including a horizontal indexing table rotatable about a vertical axis eccentric to that of said support member and having circumferentially spaced openings successively movable into registry and above said support member, a centrifugal mold separably registering with each of said openings and means for raising and lowering said support member to respectively raise and return a registering mold to said indexing table.
 8. The casting machine of claim 6 comprising a circular plate separably resting on said table in registry with each opening therein, said molds coaxially separably resting on said plates.
 9. A centrifugal casting machine comprising a vertically movable, rotatable lower clamp member, an upper clamp member positioned above said lower clamp member and rotatable coaxially with said lower clamp member and having an axial passageway therethrough, a plurality of centrifugal molds having axial sprues in the upper sections thereof, a horizontally rotatable indexing table separably supporting said molds in circumferentially spaced relationship and movable between said clamp members for conveying successive molds into coaxial registry between said clamp members, a molten metal reservoir located above said upper clamp member, nozzle communicating with said reservoir and directed toward said passageway, a valve for opening and closing said nozzle, a drive means movable between drive engagement and disengage position with said lower clamp member, and cycle sequencing means including first means for sensing the raising of said lower clamp member and the clamping of a mold between said clamp members, second means for sensing the metal level in a clamped mold, means responsive to the actuation of said first means for shifting said drive means into engage position and opening said valve, means responsive to the actuation of said second means for closing said valve and shifting said drive means to disenGage position and lower said lower clamp member.
 10. The centrifugal casting machine of claim 9 wherein said second clamp member is vertically movable between raised and normally depressed positions, and said first sensing means is responsive to the raising of said upper clamp member.
 11. The centrifugal casting machine of claim 9 including a vertical hollow shaft supporting said upper clamp member and having an axial bore delineating said passageway, said first sensing means including a pair of spaced electrodes positioned at the level of the underface of said upper clamp member in registry with said sprue.
 12. The centrifugal casting machine of claim 9 including means responsive to the raising of said lower clamp member above a predetermined level for bypassing the opening of said valve terminating said cycle.
 13. The centrifugal casting machine of claim 9 including third means located proximate the border of a clamped mold response to the ejection of metal from said mold and means responsive to the actuation of said third means for closing said valve.
 14. The centrifugal casting machine of claim 9 wherein said indexing table includes a circular base having circumferentially spaced circular openings therein and a circular support plate vertically separably positioned in each of said openings and separably supporting a corresponding mold.
 15. The centrifugal casting machine of claim 14 wherein said indexing table includes partition walls projecting upwardly from said base and delineating compartments separating said base openings and open at the periphery of said table.
 16. The centrifugal casting machine of claim 9 including a cylindrically shaped plate located along the periphery of said table proximate said clamp members and being outwardly movable and means responsive to the outward movement of said plate for closing said nozzle valve.
 17. The centrifugal casting machine of claim 9 including means positioned on the underface of said molds for actuating said second means when an inverted mold is engaged between said clamp members. 